Okay, we're going to take a look at Web basics here. By the end of this lesson, you should be able to explain the fundamentals of HTTP understand the request response model used and, frankly, all web applications. But specifically be able to read and understand a lot of the request response headers related to JE E Web applications. And then we'll break down the Uniform Resource Locator, lso known as the URL, into four key parts so what is HTTP Ii's hypertext transfer protocol. It's been the protocol of the web since the 90s and earlier, so it uses a request response model it's a client in our case usually a Web browser sends a request. The Web application running on a server processes the request and sends it back as a response in our case, that will be done from the container and a survey. Originally, it was just used to serve up static content here's your static content back your core hard coded if you will html page over time, of course, the market demand grew for more dynamic content, and we wanted to see things began to move and happen on the screen for us. Right things like Wait, I want to see my weather i want to see my stock prices those things begin to, be very much in demand and we had to work to make that happen in HTTP. So there's a couple of things you should know about HTTP one it's simple, lightweight and stateless and the big thing to focus on there is that it's stateless and that has its consequences. Well,it runs on top of TCP and IP we don't really need to be concerned with that but the thing that we do really need to know is that it's stateless and we're going to have to deal with that. So we're going to have to decide, where do we hold state do we hold it on the client or the server so if you log into my website and I want to remember your name who's responsible for that, right. The client, the server, It's certainly not going to be HTTP because HTTP is stateless a request will come across in an HTTP and it will have a choice of methods. Now get and post are the most common, and there's that's what we're going to focus on there's certainly more that you can look up on your own. But if you get the get and post, you can sort of teach yourself from there pretty easily, and then in addition to the get or post in the request, the method, we can provide parameters of adding additional data to the server side. So here I'm submitting a form that I want to put my first name and last name, and I'm going to pass that data over to the server so it can have it. And I do that through parameters in my request and then a response is, in our case, often an HTML document but it can be other in Miami types such as PDFs and other things like that. So the HTTP request is a text based command it's sent to a specific U R L and it contains again an HTTP method to get is typically used to request the pages, and a post is typically used to supply data to the server side. So I might post up a form with data on it, and this request may contain request parameters again, parameters are used to provide additional data to the server for our processing. So let's take a look at an example of one so, as you can see from here, this is a get request you can see the resource that I'm requesting, and then you can see a little bit more about what's going on. You don't certainly don't have to memorize this or anything we're going to show you the pertinent things to pay attention to from a J G standpoint. One thing that's really nice, as I can see, my host is my local host and I'm requesting this on Ports 80 80 so I know that my in this case, my Tomcat server is listening on that port. So what does a post request look like well, very similar, but as you can see, it starts out with a post I'm still mentioning the resource that I want is a capital H home here. It's been mapped to some resource on my server, and we'll see how to do that later all right, this tells you a little bit more about the content type and so on. The local host is here again, and even the content length right well, what about a response how does an HTTP response work it's often a text based response in our case Html. It includes some status codes, some that you are very familiar with almost everybody knows a 44 not found you've seen that come up, and that's just a responses since back in the header from the server via HTTP. What you may not know is, every time you have a successful page, a two 100 is sent back, and occasionally you'll run into four ones and five hundreds of any kind means some server problem. And there are a lot more of these we just wanted you to get the basic idea it's beyond the scope of our class but if you'd like to do a Web search on HTTP response headers. You can certainly learn a lot more through there or take one, of course Eras Core Web application classes. So multiple response headers also include If we're going back and forth a few times, maybe a time stamp the length of the response what are you giving back to me? And cookies, which we'll learn about later in the course as well You're you're going to be an expert with cookies by the time you're finished with this course. So what does it get response Look like It's telling me I'm sending back HTTP and by the way, it's 200 so everything went okay I'm sending you back text Html. You can even see the timestamp there, the length and so on, and you can see the server This was served up by an Apache TomEE Server well, what about a response Very, very similar. It has HTTP and then the 200 and some of the other stuff we saw now, in this case, the response included an Html document, and we're going to learn how to do this from our surveillance. Right, so this was literally sent back from the server to the browser so that it could render this information back
